A. What is Evolution? 1. Several definitions video 1 video 2 a. descent with modification (Darwin) b. change in gene frequencies within a population c. All the changes that have transformed life on earth from its earliest beginnings to the immense diversity existing today
Evolution: A Revolutionary Idea We can allow satellites, planets, suns, universe, nay whole systems of universe, to be governed by laws, but the smallest insect, we wish to be created at once by special act.
The Evidence of Change? • Fossil Record
“We must, however, acknowledge, as it seems to me, that man with all his noble qualities... still bears in his bodily frame the indelible stamp of his lowly origin.”
The Evolution of Evolutionary Thinking • Jean Baptiste Lamarck: Inheritance of Acquired Characteristics • Main Points • Organisms adapted to environment • Use and disuse • i. organisms lost parts because they did not use them — like the missing eyes & digestive system of the tapeworm • ii. Constant use leads to a larger organ: blacksmit muscles • b. Transmission or passing on of acquired characteristics
A. Historical Development 1. Jean Baptiste Lamarck 2. August Weismann a. Disproved Lamarck ideas by chopping of the tails of mice b. What? History
A. Historical Development 1. Charles Darwin a. Study theology at Cambridge b. 1831 appointed naturalist aboard the ship HMS Beagle i. mission was to create maps for the British Navy c. Darwin took surveys and collected samples of plants, animals, rocks, and fossils History
A. Historical Development 1. Charles Darwin d. Most famous observations: Galapagos Islands where he spent 2 months e. Eventually sailed around the world 1831-1835 video1 video 2 History
Evolution A. Historical Development 1. Charles Darwin f. Wrote a 200+ page thesis in 1844 outlining his theory but he did not publish WHY? g. Alfred Wallace: came to similar conclusions as Darwin in 1858 from observations collected in another area of the world h. Darwin agreed to a joint presentation with Wallace to the same scientific body. History
A. Historical Development 1. Charles Darwin a. Publishes Origin of Species in 1859 b. How does the public respond to the book? c. The first printing of the book sold out the first day History
A. 5 ideas of Darwin’s Theory 1. Overpopulation a. Organisms produce more young than will survive b. example: Fly eggs: 250 eggs by one female in one laying Baby sea turtles Praying Mantis young from one cocoon
A. 5 ideas of Darwin’s Theory 1. Overpopulation 2. Variation a. There exists in a population a large amount of variation
A. 5 ideas of Darwin’s Theory 1. Overpopulation 2. Variation 3. Struggle for existence a. What do organisms struggle for? i. Lion attack ii. gazelle attack b. Carrying Capacity: how many individuals can the environment support i. example: deer in CVNP 4. Survival of the strongest fittest a. Those that survive are the best adapted
A. 5 ideas of Darwin’s Theory b. Individuals that survive reproduce and pass on favorable traits c. “Fittest”: those that reproduce most successful i. Differential reproductive success 5. Natural Selection a. Environmental pressures select for the best adapted b. Animated example: DDT and flies
B. People who helped Darwin 1. Thomas Malthus a. minister, economist b. Wrote: Essay on Populations c. Predicted that population would grow faster than food supply d. Lead to Darwin’s idea of struggle for existence
B. People who helped Darwin 1. Charles Lyell a. geologist b. Wrote: Principles of Geology c. Proposed the idea of Uniformitarianism i. Geological processes are constant through time ii. Challenged the prevailing thought that the earth was young iii. Darwin needed large periods of time for natural selection to work iv. Uniformitarinism provided Darwin the time element needed for his theory
B. People who helped Darwin 1. Charles Lyell/ Uniformitarianism
Natural Selection: How Evolution Works Overpopulation Genetic Variation Struggle for Existence Differential Reproductive Success Selection occurs based on: • the interaction of the environment and the existing population variations • the more severe the environmental pressure, the more severe the selection process
Natural Selection: • the environment shapes or refines organisms adaptations Environmental Pressures • resources: food, water, shelter • climate: cold, hot, wet, dry • predation: how does one survive?
Evidences A. Anatomical 1. Fossils a. Remains or traces left in rock strata (layers) by previous organisms (video: becoming a fossil) b. Preserved in: rocks, bogs, tar amber, ice c. Types of preserved samples: imprints, castings, and amber
Evidences A. Anatomical 1. Fossils d. Transitional records i. Classic example: the horse e. Famous fossils • archeopteryx; • bird or reptile?
Evidences A. Anatomical 1. Fossils e. Famous fossils • Coelocanth: living fossil
Evidences A. Anatomical 1. Fossils e. Famous fossils
Evidences A. Anatomical 2. Comparative Anatomy a. Homologous structures i. Structures in different species that are similar in structure but serve different functions
Evidences A. Anatomical 2. Comparative Anatomy a. Homologous structures i. Divergent evolution • Divergent evolution • when isolated populations of a species evolve independently • adaptive radiation: evolution of many diversely adapted species from a common ancestor
adaptive radiation: evolution of many diversely adapted species from a common ancestor
Evidences A. Anatomical 2. Comparative Anatomy b. Analogous structures i. Structures shared by different species that serve the same function but look different • example: wings of birds and insects • example: streamline body of fish and aquatic mammals • example: cactus/euphobia
Evidences A. Anatomical 2. Comparative Anatomy b. Analogous structures ii. Convergent evolution • different species being “shaped” by similar environmental pressures Species a Species b Time
Evidences A. Anatomical 1. Vestigial structures a. Inherited organs or parts of organs that are reduced in size or non-functional Examples? i. appendix ii. coccyx iii. wisdom teeth iv. ear muscles
Evidences A. Anatomical 1. Vestigial structures iv. Whales and pythons: vestigial hind limbs v. Flightless birds: vestigial wings vi. Blind, cave dwelling animals-vestigial eyes
Evidences B. Embyrological evidence 1. def: related species exhibit similar embryological development • Found in all vertebrate embryos a. segmented muscles b. gill pouches • All of these structures are found in fish c. tubular heart: no chambers d. Aortic arches in gill region Ernst Haeckel
Evidences C. Molecular Evidence question: what on the molecular level would suggest relationships between species? 1. DNA a. the more similar the DNA: i. common proteins ii. common biochemical pathways WHY?
Evidences C. Molecular Evidence 1. DNA How similar? a. 96 – 99% similarity in sequences
Evidences C. Molecular Evidence 1. DNA b. Found in every organism: from bacteria to “man” c. cytochrome C: found in every aerobic organism / involved with making energy video
Evidences C. Co-evolution 1. def: species that co-evolve a. bacteria and humans b. ants, fungus, and bacteria D. Biogeography 1. def: study of the distribution of life around the world WHY? a. example: emus, ostriches, rhea and extinct elephant bird all found in the southern hemisphere
Evidences C. Co-evolution Examples
Evidences E. Microevolution 1. def: small changes in variations or gene frequencies occurring in a population of organisms 2. Classic example: Industrial Melanism a. def: The darkening of several species of moths during the period of industrialization in many countries by the spread of a gene controlling elevated melanin synthesis
Evidences 2. Classic example: Industrial Melanism a. The selective pressure came from predators (insect eating birds). The moth’s color provides camouflage. b. Moths rest during the daytime on trees.c. In rural areas where the air is clean the trees are covered in lichen. d. The peppered variety is better camouflaged when it rests on these trees. The melanic form is easily seen.e. In industrial areas air is polluted and the lichens die. f. The tree trunks may also be covered in soot giving a black background. g. This favors the melanic form giving them a selective advantage.
Evidences 3.Other examples a. evolution of antibiotic resistant forms of bacteria b. evolution of insecticide resistant insects (DDT and flies)
Evidences F. Artificial Selection 1. Def: Selection of desirable traits by man to create organisms with “improved” genetics or desirable traits
Evidences F. Artificial Selection: plant selection
Two Modes of Evolution 1. Microevolution: Small changes within a population or gene pool or shift in gene frequencies 2. Macroevolution: The formation of new species from other species The question is: What defines a species?